Those are the only plugins in my collection for which I'm not able to show their GUI. They still work tho, I'm able to use the generic ardour controls editor.
Those plugins work fine in standalone and under the hosts Carla and Qtractor.
Ardour log returns : [ERROR]: failed to instantiate LV2 GUI
everytime I try to fire up the GUI.
They are qt-based (Qt version 5.5.1.) .
The version of the plugins is 0.8.0 and have been installed with apt through the KXStudio repository. They were working fine under ardour in the previous versions.

Steps To Reproduce

1) Get the packages samplv1 samplv1-lv2 drumkv1 drumkv1-lv2 from the Kxstudio repository
2) Create a new MIDI track or AUDIO + MIDI track with one of those plugins.
3) Try to fire up the GUI or see if it's automatically opens.

I installed ardour through the KXStudio repository.
I think you are right about libsuil but the package is already installed on my computer. When running ardour from command line, this line appears when I try to fire up the GUI :
suil error: Unable to open wrap module /opt/ardour/lib/libsuil_qt5_in_gtk2.so (/usr/lib/x86_64-linux-gnu/libQt5Core.so.5: version `Qt_5.7' not found (required by /opt/ardour/lib/libsuil_qt5_in_gtk2.so))
I then noticed that my version of Qt was 5.5 so I installed Qt 5.7 from the official site but it didnt change anything.